1. Technical Field
The present invention relates to a solid-state image pickup device that converts incident light into an electric signal.
2. Related Art
In medical image diagnosis, nondestructive testing, and the like, an image is picked up by using a radiation ray such as an X-ray. However, it is difficult to implement a scaling-down optical system in photographing using a radiation ray, and accordingly, image pickup at the same magnification is needed. Accordingly, in medical image diagnosis, nondestructive testing, and the like, an image pickup surface having a large size is required. Thus, solid-state image pickup devices in which a plurality of pixels is configured in a matrix shape by depositing various thin films on a substrate formed of glass or the like are used. In addition, when a two-dimensional image sensor is configured by using the solid-state image pickup device, an image pickup surface having a large size is required. Accordingly, in such a case, a plurality of pixels is configured in a matrix shape by depositing various thin films on a substrate formed of glass or the like.
In particular, for example, as shown in FIG. 15, a plurality of scanning lines 3a that extends in direction X, a plurality of data lines 6a that extends in direction Y that intersects the plurality of scanning lines 3a, and a plurality of bias lines 5a that is disposed in parallel with the data lines 6a are included within an image pickup area 100c of a base substrate 10. In addition, in positions corresponding to intersections of the scanning lines 3a and the data lines 6a, a plurality of pixels 100a is disposed. In addition, in each of the plurality of pixels 100a, a field effect transistor 30 that is controlled by the scanning line 3a and a photoelectric conversion element 80 that is formed of a PIN photo diode electrically connected to the data line 6a through the field effect transistor 30 are formed. Here, the photoelectric conversion element 80 is connected also to the bias line 5a, and accordingly, a reverse bias is applied to the photoelectric conversion element 80. Thus, when the field effect transistor 30 is turned on or off in accordance with a scanning signal that is supplied through the scanning line 3a, a signal corresponding to electric charges accumulated in each pixel 100a can be detected through the data line 6a (see Japanese Patent No. 3144091).
The configuration shown in FIG. 15 is an example for comparison with an embodiment of the invention and is not general technology.
In the solid-state image pickup device, in the middle of a manufacture process or in any finished product state after completion of the manufacture process, electrostatic breakdown can easily occur due to the influence of static electricity that is penetrated into the pixel 100a through a wiring. However, any propose for protection of the solid-state image pickup device from the static electricity has not been made.
There is a liquid crystal device as a device in which a plurality of pixels is disposed in a matrix shape. In the liquid crystal device, a configuration in which the scanning line and the data line are electrically connected to a constant electric potential line through protection diodes has been proposed for protection of the device from static electricity. Accordingly, when a countermeasure for electrostatic protection employed in the liquid crystal device is applied to the solid-state image pickup device, the solid-state image pickup device can be protected from static electricity.
However, there is a problem that occurrence of electrostatic breakdown due to the influence of static electricity cannot be protected even in a case where the countermeasure for electrostatic protection that is employed in the liquid crystal device is applied to the solid-state image pickup device.